jerry gollnick

Ok, I've confused myself again. I saw a posting that said the C3 camber bracket was redesigned to allow for use of wider tires and lower the roll center of the rear. When I look at the bracket it appears to raise the inner mounting point for the camber rod up from ground level. All things being equal this would create a greater angle downward from the differential to the bearing carrier. It does move the pivot point for the half shaft and the camber rod closer together thereby potentialy reducing the effect of camber change due to suspension compression but while doing this I think it actually raises the roll center. As I said I'm confused again.
Bill Mitchell and I worked on C2/3 rear suspension geometry and it is deceptivly complicated. Can anydody shed some light on why GM made the Camber strute rod brackt change for C3

Donny Brass

As far as I know, the change decreased the camber change through the compression cycle of the rear suspension


I run the c3 bracket and a spacer under it to lessen the camber change at launch

Scott Marzahl

According to Guldstrand, the C3 bracket increases camber gain for the C2 which increases tire bite. I'm running one on my '67 as well.

TCracingCA

The bracket for 63-68 is 1" higher mounting the inner camber rods higher, thus changing to the later bracket drops the geometry 1" lessening the angle, but many have found the geometry angle even better with one more inch of drop by different methods like a camber block or designing their own bracket unit like Herb adams did and the Toms Differential, and Global west, Greenwood, units etc who further changed the bracket and actually Guldstrand never developed a custom bracketl . Basically making them (camber rods) parallel to the attachment on the bearing hub bracket for the camber rod attachment. Therefore as the wheel moves up and down, you would have less camber change basically starting at 0 degrees to the attachment height level. The bracket itself doesn't change roll center essentially on it's own, but the better camber rod angle in conjunction with setting height with the spring bolts and changing the trailing arm geometry could lead to the ability through adjustment to change roll center, unless you have fixed length strut rods (camber rods). You are also trying to get the angle or better put "plane of the upper link of the suspension (the halfshafts parallel) to the camber rods. Therefore gaining better contol over the range of travel bettering the camber curve during suspension movement. I hope I got that said OK, because I was trying to write it as simplified as possible! Also you can help or hurt corner weighting with the spring bolt adjustments while aligning everything. I do think leveling the halfshafts is crucial, not only for coupling strength, but that essentially being an upper a-arm, it is not good for something coming in at an angle and moving differently from an angle with the wheel uprights. You want the arc of everything to move in unison as much as possible to limit camber changes through suspension changes caused by the tire tracking unless you are doing something where you are trying to set more camber based on a track situation induced by cornering forces! For tonight, I am not going to try to explain raising the diff by mod of the crossmember by compression of the donuts or shaving the donuts or elimination of thde donuts. Thus you raise that the halfshaft angle changes again and now you have to go outboard to the upright to adjust those, while reworrying about the camber rods. For the true benefit of the brackets we are discussing it is best to run adjustable heims for locking everything because the stock rubber has deflection and the cam setups don't help in high cornering loads! Alot to think about back there!

jerry gollnick

You can see from this thread some people think the C3 bracket increases camber gain and some think it reduces it.
I dont think it increases camber gain becasue that is not something Zora would have done intentionally.
TR i agree with your logic BUT the C3 bracket actually moves the camber rod inner attachment point upward not downward.
For someone to run the C3 bracket and then use a spacer under the mount defeats the change made in the C3 bracket.
THe half shaft and the camber rods set the instantaneous roll center so moving these angles is potentially a big deal.
I run my halfshafts horizontal and my camber rods( which are heim jointed) pointing downward at about 10 degrees. I use the C2 camber bracket.
What GM did with the C3 bracket doesn't make sence to me.
I going to have to get the card board out again and make some models and move them through travel to figure out if I'm as confused as I think I am.

robert miller

jerry gollnick

This may be true but I don't see how reducing the contact patch size by increasing camber gain helps traction

Thorson

Not a very good picture, but does show that the C3 bracket lowers the inner mounting point by about an inch.

jim lockwood

Lowering the inner mount point (meaning: moving it closer to the ground as on C3 suspension) reduces the amount of camber gain during body roll. That can be helpful in keeping the tire perpendicular to the road surface and the tread in full contact with the road when running wide rear tires.

jerry gollnick

The brackets shown look to me like they bolt up to the bottom of the differential carrier on the LEFT side of the bracket as shown so the lower bracket raises the inner camberrod pivot point. am I looking at this incorrect?

jerry gollnick

Thorson

Yes, that's right. The C2 bracket is the lower one in the pic.
Here's another, C2 is on the left.

jerry gollnick

now THAT makes sence. Thankyou. I was sent a photo earlier and asked why I wasnt using the new improved C3 bracket on my racecar. The Bracket was incorrectly idenetified as C3 when it was in reality a C2. Mystery solved. Thankyou.

sub006

Was the C3 geometry changed after the first decade or so of production, along with other modificatons to the rear end? I'm not sure '82 parts interchange with '68, for example.

TCracingCA

Yes Drop when going to the C3 bracket. Now Jerry, I do want to see the back end (rod angles, halfshafts and spring bolt lengths of adjustment in a picture). I probably do have pictures of the underside of your car already, because I do alot of that in the pits at the races (photograph other guys suspensions). But as with the Guldstrand thought, he settled on the C3 bracket as good enough for the geometry, whereas other guys took it a little farther, but then he had the 5 link offering, so why go with an added 1" drop, or a spacer could just be added. But overall they have calculated with the 1" drop the ability to tune in a 2" roll Center drop.

I will see if I can get a picture up of the suspension on my Father's car, since my racer is apart, and my 1968 doesn't have all of the race bells and whistles or find a picture to post where it is level (everything).

Herb Adams 2" drop picture (sorry for the flash), but rods level 0 degrees and halfshafts level!



Next I should be able to get a pic up of a Guldstrand setup using these stock C3 brackets! Also have to remember amateur racing and for street, you had to run some semblance of stock for the rules or for streetability! And if you want full race, go multi-link so his offerings were smart, where Adams, Global West and others were still evolving the dinosaur!


The 1968 year was the transition period, and I am sure someone will dispute this, but 1968's early still had the C2 bracket and the later 68 had the C3 bracket.

Thus to answer the new question. Which 1968 bracket you are talking about is important to which would interchange with the 1982.

jim lockwood

I bet they don't. By '82 the differential was aluminum and the spring was fiberglass. Probably several other things had to be modified to accommodate those changes.

C2Racer

So what is Dick selling here:

http://www.guldstrand.com/scripts/pr...p?idproduct=97

A C3 bracket? I have one on my race car and increased camber is what I want in the turns.

Steve

Thorson

That looks exactly like the one I got from Tom's Differentials, part VCRB. It's a repro of the C3 bracket. Tom also has VCRB-MOD which drops the mounting point an additional inch.
I had a screw up on some orders and ended up getting and using a refurbished original C3 bracket. Same as the Tom's and Guldstrands units except for that small tab.

jerry gollnick

Well the lowering may increase the gain of the camber ROD but what your going for is the NET between the arch the 1/2 shaft traces and the arch the camber rod traces. I want very small changes in camber from my static setup.

jerry gollnick

Based on testing I've done you do not want the 1/2 shaft higher outboard higher than inboard.